Projection of plane figure: put the cup on a plane and observe the projection of the cup on the plane, and you can draw a mathematical figure. For example, you can measure the projection of a cup on a plane with a ruler and protractor, and draw the corresponding figure according to the measurement results. This method is suitable for plane graphics, such as circles, rectangles and triangles.
Development of three-dimensional graphics: If you want to draw a three-dimensional graphic of a cup, you can expand the cup into a plane graphic. First of all, take apart the various parts of the cup and spread it into a graph on a plane. Then, you can draw a mathematical figure according to the expanded figure. This method is suitable for three-dimensional graphics, such as cylinders and cones.